fix(mobile): remove Android Threads page T3 Code branding

[PixPMusic]

Summary

• replace the branded Android Threads header with the plain Threads title used by iOS today
• align the header and compact thread list through one shared horizontal inset
• preserve the heading semantics for accessibility

Tracks the history and decision in #4864.

Important

This is the mutually exclusive alternative to #4862. If this direction is selected, close #4862 and #4861. Do not merge both branding-direction proposals.

Why

Android gained a T3 Code lockup in #3774, while the final commit in #4163 later removed the equivalent iOS lockup. If the intended mobile direction is a plain page title, Android should match iOS rather than carrying a platform-only brand treatment.

Before / After

Android

Before	After

The comparison uses the deterministic dark-mode Threads fixture with no popup.

Verification

• vp run --filter @t3tools/mobile typecheck
• targeted formatting and git diff --check
• deterministic dark-mode Threads capture on the Android emulator

Checklist

• This PR is small and focused
• I explained what changed and why
• I included before/after UI evidence
• I preserved an accessible Threads heading

Model: GPT-5.6 Sol | Harness: Codex in T3 Code

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Note

Replace Android home header wordmark with plain 'Threads' title

• Replaces the T3Wordmark + 'Code' label + 'Alpha' badge in AndroidHomeHeader with a plain RNText title reading 'Threads', marked as accessibilityRole='header'.
• Extracts HOME_HORIZONTAL_INSET = 20 into a shared layoutMetrics module and uses it for both the header padding and THREAD_LIST_COMPACT_INSET (previously a literal 20).

^{Macroscope summarized 5ee95cc.}

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[PixPMusic]

@macroscope-app please refresh the PR summary in the description markers.

[macroscopeapp]

Sorry, I'm unable to act on this request because you do not have permissions within this repository.

[PixPMusic]

Julius confirmed that the issue was that the merged branding in iOS was breaking a visual effect.
The other two PRs in this series have been updated to fix this.